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NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 159 ABBREVIATIONS Abbreviation Term 4U Four-lane undivided 5T Four lanes and a TWLTL AADT Annual average daily traffic (veh/d) AADTR AADT estimate from FHWA HPMS or SEMCOG system-wide data rounded to nearest 10 AASHTO American Association of State Highway and Transportation Officials Abs(PSLâAvg) Absolute value of posted speed limit minus average speed (mph) AccessDen Data for DrvUsigPerMileBoth regrouped into three levels: LT40=less than 40 driveways/unsignalized intersections per mile, 40to60=between 40 and 60 driveways/unsignalized intersections per mile, and GT60=greater than 60 driveways/unsignalized intersections per mile ACUB Adjusted census urban boundary ADA Americans with Disabilities Act ADT Average daily traffic Beg_IT_Legs Number of legs for intersection at beginning of segment BIC Bayesian information criterion Bike_1yes Bike lane presence: 1=yes, 0=no Bike_Lane Bike lane presence: 1=yes, 0=no Bus Bus stop presence collected via âPlacesâ in Google Earth: 1=yes, 0=no C50 The 5-mph increment that is closest to the 50th percentile speed C85 The 5-mph increment that is closest to the 85th percentile speed CBD Central business district CMF Crash modification factor CoefVar Coefficient of variation of speed CRIS Crash Records Information System Curb_1yes Is curb present (for at least 50% of segment): yes=1, no=0 Develop Development: Com/Ret/Ind (for commercial, retail, or industrial), Residential, or Rural/Parks (for areas with park-like or rural-like settings) DOT Department of transportation DrvUsigPerMileBoth Per mile rate for driveways (residential and commercial) and public intersections along the segment in both directions End_IT_Legs Number of legs for intersection at ending of segment F&I Fatal and injury crashes (KABC) FCS Functional classification system FHWA Federal Highway Administration ft Feet FuncClass Revised National Functional Class Code GEE Generalized estimating equations GLM Generalized linear model GPS Global positioning system HCM Highway Capacity Manual Horz_1tan Horizontal alignment: 1=straight (tangent), 0=some horizontal curvature
NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 160 Abbreviation Term HPMS Highway Performance Monitoring System HSIS Highway Safety Information System HSM Highway Safety Manual Int_Type1 Description of End Point #1: signal, all-way stop, stop, roundabout, or other break point Int_Type2 Description of End Point #2: signal, all-way stop, stop, roundabout, or other break point ISW Inside shoulder width (ft) K Constant associated with the confidence level (1.645 for 95% confidence) KABC Fatal and injury crash severity levels KABCO All crash severity levels km/h Kilometers per hour Len_mi Segment length (mi) LnWdG Lane width (ft) for the segment grouped into: N=Narrow (7, 8, 9, or 10 ft), T=Typ (11 or 12 ft), W=Wide (13 ft or more) LOS Level of service LW Lane width M Exposure (100 million vehicle miles) Median Median type: none (undivided), raised (also depressed), TWLTL (also delineated) MedWidth Typical or average median width for the segment (ft) MGF Michigan Geographic Framework mi Miles mph Miles per hour MPO Metropolitan planning organization MSP Michigan State Police MSU Michigan State University MUTCD Manual on Uniform Traffic Control Devices MVM Million vehicle miles N Number of lanes NACTO National Association of City Transportation Officials NB Negative binomial NCHRP National Cooperative Highway Research Program NCUTCD National Committee on Uniform Traffic Control Device NDS Naturalistic Driving Study NID Not intersection and driveway NPMRDS National Performance Management Research Data Set NTSB National Transportation Safety Board Num_Lanes Number of through lanes (not including exclusive turn lanes) NumSigInt Number of signalized intersections along segment, including the signals at the begin or end of the segment OnStreet_Parking On-street parking: yes=1 or no=0 Pace Percent of vehicles in 10-mph pace for the site (%) Pace_Bin Range of the pace
NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 161 Abbreviation Term Pace_LV Lower speed value of 10-mph pace for the site Pace_Per Percent of vehicles in 10-mph pace for the site Pace_UV Upper speed value of 10-mph pace for the site PDO Property damage only PedAuto Typical or average distance between the sidewalk and the automobile lane for the segment, sum of the following (when present): parking width, bike width, bike-auto separation, and sidewalk to road separation (ft) PedCross_1yes Is a midblock marked pedestrian crossing present within the segment: 1=yes or 0=no PerOverPSL Percent of observations over the speed limit for the site (%) PerOvPSL Percent of observations over the speed limit for the site (%) POSTED_SPE Posted speed limit per SEMCOG system-wide data PROWAG Public Rights-of-Way Accessibility Guidelines PSL Posted speed limit (mph) PSLâAvg Posted speed limit minus average speed (mph) PSLMinusSped85 Posted speed limit minus 85th percentile speed (mph) PSLâS85 Posted speed limit minus 85th percentile speed (mph) Ra Average crash rate for a given road type, provided by the user or obtained from HSIS tables Rc Critical crash rate for a given road type RD50 The 5-mph increment obtained by rounding down the 50th percentile to the nearest 5-mph increment RD85 The 5-mph increment obtained by rounding down the 85th percentile to the nearest 5-mph increment RHiNO Roadway Highway Inventory Network Offload RHR Roadside hazard rating RoadSurf Distance between the driving surface edges, calculated as number of through lanes multiplied by average lane width plus median width plus parking widths plus bike widths RTS On-road tube site RU_F_SYSTEM TxDOT functional classification for street: U3=Urban Other Principal Arterial, U4=Urban Minor Arterial, U5=Urban Major Collector, U6=Urban Minor Collector, U7=Urban Local RW Regulatory and Warning Signs Technical Committee S85âAvg 85th percentile speed minus average speed (mph) School School zone presence collected via âPlacesâ in Google Earth: 1=yes, 0=no SchZone_1yes School zone presence: 1=yes, 0=no SEM Structural equation modeling SEMCOG Southeast Michigan Council of Government SHRP2 Second Strategic Highway Research Program Sidewalk_1yes Is a sidewalk present within the segment: 1=yes or 0=no Site Unique name for each site, consist of a segment number plus the primary direction for traffic (e.g., NB, SB, EB, or WB)
NCHRP Web-Only Document 291: Development of a Posted Speed Limit Setting Procedure and Tool 162 Abbreviation Term SLSG Speed Limit Setting Group SLS-Procedure Speed Limit Setting Procedure SLS-Tool Speed Limit Setting Tool Spd85 85th percentile speed (mph) SpdAve Average speed for the site (mph) SpdAve Average speed (mph) SpdAve_Hr_Ca.Qa Average speed per hour per site for both the City of Austin traffic count data and the data collected as part of this research (mph) SPF Safety performance functions SSL Suggested speed limit StdSpd Standard deviation of speeds for the site (mph) SW Shoulder width TCD Traffic control device TRB Transportation Research Board trk/hr Trucks per hour TTI Texas A&M Transportation Institute TWLTL Two-way left-turn lane TxDOT Texas Department of Transportation U3 Urban Other Principal Arterial U4 Urban Minor Arterial U5 Urban Major Collector U6 Urban Minor Collector veh/d Vehicles per day VMT Vehicle miles traveled Vol_Day Volume per day in both directions vph Vehicles per hour